1. Field of the Invention
The present invention relates to a binary image data extracting a system and method for extracting part of large image data in a binary image compression/expansion apparatus.
2. Description of the Related Art
A binary image compression/expansion apparatus handling a great amount of binary image data usually encodes binary image data to speed up the data transfer. Typical coding systems used for this type of apparatus are the MH (Modified Huffman) system, MR (Modified Read) system and MMR (Modified MR) system.
To extract part of image data from a binary image coded by the MH, MR or MMR coding system, all code data are expanded and developed into the original image before the extraction.
According to the above method, however, a large amount of image data which does not directly concern the extraction must be developed. As the original image becomes larger, therefore, image expansion takes more time, and the image memory needs a larger capacity.
Examined Japanese Patent Publication No. 63-33350 discloses a method for dividing a binary image into segments and encoding a head line of each segment in the one-dimensional coding system. This method cannot however be used with the MMR system which encodes binary image data with every line having a correlation with multiple lines. This method also cannot cope with the MR system if the head line of each segment is coded in a two-dimensional coding system.